Climate Prediction Center

US HAZARDS ASSESSMENT
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
300 PM EST NOVEMBER 20 2009

SYNOPSIS: A SERIES OF COLD FRONTS ARE EXPECTED TO ENTER THE PACIFIC NORTHWEST AND MOVE EASTWARD ACROSS THE LOWER 48 STATES OVER THE NEXT WEEK, BRINGING WET WEATHER TO PARTS OF THE US. SURFACE HIGH PRESSURE IS FORECAST ACROSS THE WESTERN HALF OF THE COUNTRY EXCEPT FOR THE PERIODIC PASSAGE OF THE COLD FRONTS. A SURFACE LOW PRESSURE SYSTEM IS FORECAST TO MOVE ONTO THE COAST OF CAPE HATTERAS EARLY IN THE PERIOD AND TRAVEL NORTHWARD ALONG THE EAST COAST, BRINGING RAIN TO COASTAL AND INLAND AREAS. A SERIES OF SURFACE LOW PRESSURE SYSTEMS ARE ANTICIPATED TO LEAD TO STORMY CONDITIONS ACROSS THE SOUTHERN COAST OF ALASKA, ALASKAN PANHANDLE AND THE ALEUTIANS.

HAZARDS

HIGH WINDS AND HIGH WAVES ACROSS THE SOUTHERN COAST OF ALASKA AND THE ALEUTIANS NOVEMBER 25-27.
HEAVY SNOW FOR THE ALASKAN PANHANDLE NOVEMBER 23-25.
HIGH WINDS AND HIGH WAVES FOR THE ALASKAN PANHANDLE NOVEMBER 23-26.
HIGH WINDS FOR THE PACIFIC NORTHWEST NOVEMBER 23.
HEAVY PRECIPITATION ACROSS PARTS OF THE UPPER MIDWEST NOVEMBER 23-24.
ONGOING FLOODING FOR PARTS OF SOUTH DAKOTA, MISSOURI, THE LOWER MISSISSIPPI VALLEY, AND SOUTHEASTERN TEXAS.
SEVERE DROUGHT IN PARTS OF WISCONSIN, TEXAS, AND AREAS IN THE WESTERN U.S. SOME RELIEF IS EXPECTED ACROSS ALL THESE AREAS, EXCLUDING AREAS IN ARIZONA, SOUTHERN CALIFORNIA, AND NEVADA.

DETAILED SUMMARY

FOR MONDAY NOVEMBER 23 - WEDNESDAY NOVEMBER 25: A SURFACE LOW PRESSURE SYSTEM IS PREDICTED TO MOVE ALONG THE COAST OF CAPE HATTERAS EARLY IN THE PERIOD AND TRACK NORTHWARD ALONG THE EAST COAST. LOCALIZED AREAS ALONG THE EAST COAST COULD RECEIVE HEAVY PRECIPITATION. MODEL UNCERTAINTY PRECLUDES DETERMINING SPECIFIC AREAS IMPACTED BY HEAVY PRECIPITATION AT THIS TIME.

AN AMPLIFIED UPPER-LEVEL TROUGH IS PROGGED TO TRAVERSE THE CENTRAL AND EASTERN CONUS. A SURFACE LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE SOUTHERN PLAINS AHEAD OF THIS TROUGH AND PROPAGATE NORTHEASTWARD, REACHING THE UPPER GREAT LAKES BY THE END OF NEXT WEEK. THIS STORM MAY BRING HEAVY RAIN AND SNOW TO PORTIONS OF THE UPPER MIDWEST.

ANTECEDENT AND EXPECTED UPCOMING PRECIPITATION FROM THE PASSAGE OF COLD FRONTS AND STORM SYSTEMS WILL LIKELY EXACERBATE AND CONTINUE THE FLOOD CONDITIONS ACROSS SOUTHEASTERN TEXAS, THE LOWER MISSISSIPPI VALLEY, MISSOURI, AND SOUTH DAKOTA.

A SERIES OF SURFACE LOW PRESSURE SYSTEMS ARE FORECAST TO PROPAGATE ACROSS THE GULF OF ALASKA, BRINGING STORMY WEATHER TO THE SOUTHERN COAST OF ALASKA, ALASKAN PANHANDLE, AND THE ALEUTIANS. THE PACIFIC NORTHWEST COULD EXPERIENCE HIGH WINDS ASSOCIATED WITH THESE SURFACE LOW PRESSURE SYSTEMS AT THE BEGINNING OF THIS PERIOD.

A STRONG STORM SYSTEM IN THE GULF OF ALASKA IS ANTICIPATED TO BRING HIGH WINDS AND HIGH WAVES TO PARTS OF THE ALASKAN PANHANDLE DURING THIS PERIOD INTO THE BEGINNING OF THE 6-10 DAY PERIOD. THE ALASKAN PANHANDLE MAY ALSO RECEIVE HEAVY SNOW ASSOCIATED WITH THIS STORM. LATER ON IN THE PERIOD, ANOTHER STRONG STORM IN THE GULF OF ALASKA IS EXPECTED TO BRING HIGH WINDS AND HIGH WAVES TO THE SOUTHERN COAST OF ALASKA AND PARTS OF THE ALEUTIANS.

TROPICAL RAINFALL ASSOCIATED WITH THE CURRENT MJO IS LIKELY TO RESULT IN AN EXTENSION OF THE PACIFIC JET SO THAT DURING THIS PERIOD, ABOVE MEDIAN PRECIPITATION (INCLUDING POTENTIAL HEAVY RAIN EVENTS) IS MORE LIKELY FOR AREAS ALONG THE WEST COAST FROM WASHINGTON TO CENTRAL CALIFORNIA.

FOR THURSDAY NOVEMBER 26 - MONDAY NOVEMBER 30: THE STORM SYSTEM IN THE UPPER MID-WEST FROM THE 3-5 DAY PERIOD IS ANTICIPATED TO EXIT THE COUNTRY INTO CANADA WHILE THE SURFACE LOW PRESSURE SYSTEM ALONG THE EAST COAST IS FORECAST TO EXIT THE NORTHEAST. THESE AREAS MAY RECEIVE PRECIPITATION ASSOCIATED WITH THE REMNANTS OF THESE STORMS.

MOST MODELS INDICATE AN AMPLIFIED UPPER-LEVEL TROUGH PROPAGATING ACROSS THE EASTERN HALF OF THE COUNTRY EARLY IN THE PERIOD. UPSTREAM, A SERIES OF UPPER-LEVEL SHORTWAVES ARE FORECAST TO ENTER THE PACIFIC NORTHWEST AND PROPAGATE EASTWARD. SIGNIFICANT MODEL DIFFERENCES REGARDING THESE SHORTWAVES PRECLUDES DETERMINING SPECIFIC HAZARDS ASSOCIATED WITH THEM.

A SERIES OF STRONG STORM SYSTEMS IN THE GULF OF ALASKA IS ANTICIPATED TO EXTEND THE HAZARD OF HIGH WINDS AND HIGH WAVES FOR THE SOUTHERN COAST OF ALASKA AND THE ALEUTIANS FROM THE 3-5 DAY PERIOD INTO THE END OF NEXT WEEK. COASTAL AND OFFSHORE AREAS COULD EXPERIENCE WINDS OF OVER 35 KNOTS AND WAVES OF OVER 20 FEET.

FOR TUESDAY DECEMBER 01 - FRIDAY DECEMBER 04: THE 6Z OPERATIONAL GFS INDICATES THE DEVELOPMENT OF A STRONG CUTOFF LOW ACROSS THE MISSISSIPPI VALLEY AND CONTINUED UPPER-LEVEL TROUGHS ENTERING THE PACIFIC NORTHWEST DURING THIS PERIOD. DUE TO THE INHERENT UNCERTAINTY OF MODELS AT THIS TIME, NO HAZARDS CAN BE DETAILED EXCEPT FOR LONG-TERM SEVERE DROUGHT.

ABOVE NORMAL PRECIPITATION ACROSS WASHINGTON, OREGON, AND NORTHERN AND CENTRAL CALIFORNIA COULD EXTEND INTO THIS TIME PERIOD FROM THE 6-10 DAY PERIOD ASSOCIATED WITH THE TYPICAL WEATHER PATTERN EXPECTED FROM MJO EVENTS.

SEVERE DROUGHT IS EXPECTED TO CONTINUE IN PARTS OF WISCONSIN, TEXAS, AND AREAS IN THE WESTERN U.S. SOME RELIEF IS EXPECTED ACROSS ALL THESE AREAS, EXCLUDING AREAS IN ARIZONA, SOUTHERN CALIFORNIA, AND NEVADA.

FORECASTER: MELISSA OU

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